Facile one-pot synthesis of uniform niobium-doped titanium dioxide microparticles for nanostructured dye-sensitized solar cells

In this study, we present the deposition of uniform sponge-like films using a novel niobium-stabilised TiO₂ gel for dye-sensitized solar cells (DSCs) applications. The introduction of Nb into TiO₂ lattice limits the transformation from anatase to rutile phase, stabilising anatase nanoparticles. The films are composed of uniform spherical particles with diameter around 3 μm, containing small nanoparticles with the average grain size of 40 nm, deposited by dip coating method. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) reveal that Nb⁵⁺ is well incorporated into the titania crystal lattice without forming specific niobium phases. UV–Visible spectra show that the doped-TiO₂ films have lower band gap energy than that of undoped-TiO₂, extending the absorption of TiO₂ into visible region. Diffuse reflectance spectroscopy (DRS) shows that the presence of rutile nanoparticles in photoanodes may improve the photovoltaic performance of solar cells due to better light scattering ability of rutile than anatase phase. The DSC stabilised with 3 at. % Nb (i.e., PN3) had the highest power conversion efficiency of 7.38 % as a result of less recombination, which is demonstrated by electrochemical impedance spectroscopy (EIS).     

Photoluminescence characteristics of Y3Al5O12:Tb3+ phosphors synthesized using the combustion method

For this study, terbium-doped yttrium aluminum garnet (YAG:Tb) phosphor powders were prepared via the combustion process using the 1:1 ratio of metal ions to reagents. The characteristics of the synthesized nano powder were investigated by means of X-ray diffraction (XRD), scanning electron microscope (SEM), and photoluminescence. Single-phase cubic YAG:Tb crystalline powder was obtained at 800 °C by directly crystallizing it from amorphous materials, as determined by XRD techniques. There were no intermediate phases such as yttrium aluminum perovskite (YAlO₃) and yttrium aluminum monoclinic (Y₄Al₂O₉) observed in the sintering process. The SEM image showed that the resulting YAG:Tb powders had uniform sizes and good homogeneity. With the increase in the sintering temperature, the grain size increased. The photoluminescence spectra of the YAG:Tb nanoparticles were investigated to determine the energy level of electron transition related to luminescence processes. There were three peaks in the excited spectrum, and the major one was a broad band of around 274 nm. Also, the YAG:Tb nanoparticles showed two emission peaks in the range of 450?×?500 and 525?×?560 nm, respectively, and had maximum intensity at 545 nm.     

Sol-gel Synthesis and Photoluminescence Characterization of Ba2SiO4:Eu2+ Green Phosphors for White-LED Application

In this paper, Ba₂SiO₄:Eu²⁺ green phosphor was synthesized by sol-gel method. TGA-DTA, XRD, SEM and PL spectra were used to characterize the as-prepared phosphors. The phosphors are composed of nanoparticles with 60 nm grain size and exhibit green light with a broad peak around 500 nm. The relationship between crystal growth, morphology and luminescent properties was studied. The structure and luminescence properties of phosphors synthesized in different conditions were also discussed.     

Size dependence of THz region dielectric properties for barium titanate fine particles

Barium titanate (BaTiO₃) crystallites with various particle sizes from 22 to 500 nm were prepared by the two-step thermal decomposition method of barium titanyl oxalate. Various characterizations revealed that these particles were impurity-free, defect-free, dense BaTiO₃ particles. The powder dielectric measurement clarified that the dielectric constant of BaTiO₃ particles with a size of around 58 nm exhibited a maximum of over 15,000. To explain this size dependence, the THz region dielectric properties of BaTiO₃ fine particles, especially Slater mode frequency, were measured using the far infrared (FIR) reflection method. As the result, the lowest Slater mode frequency was obtained at 58 nm. This tendency was completely consistent with particle size dependence of the dielectric constant.     

Ferroelectric phase transitions in sodium nitrite nanocomposites

The structure and dielectric properties of sodium nitrite and its solid solutions confined in porous glasses have been studied. The temperature dependences of the order parameter and the unit cell volume for NaNO₂ embedded into porous glasses with different pore sizes were studied by neutron diffraction in the ferro- and paraelectric phases. The characteristic sizes of nanoparticles are determined. It is shown that at a size of nanoparticles smaller than ~50 nm a crossover of the phase transition from first order to second order is observed. The effect of doping of sodium nitrite with potassium nitrite on the dielectric properties of the nanocomposite materials was studied and a strong lowering of the dielectric losses was observed.     

Highly luminescent CdSe nanoparticles embedded in silica thin films

Thin films of luminescent CdSe nanoparticles with and without silica capping were prepared using sol-gel method. The blue shift observed in the optical absorption spectra suggested quantum confinement effect in the prepared films. The films showed photoluminescence emission in the range of 510–590 nm depending upon the particle size of CdSe particles. The emission intensity increased when CdSe particles were embedded in silica matrix. The emission intensity was found to decrease with aging for the films containing CdSe particles without silica capping when they were exposed in relatively humid air (relative humidity 80%). The films containing CdSe nanoparticles embedded in silica matrix showed more stable behavior. The emission intensity practically remained constant with aging in humid atmosphere.     

Neodymium substituted Bi4Ti3O12 nanostructures through self-assembly

For the sake of fabricating the ultrahigh density ultralarge scale integration (ULSI) memory chips, the ferroelectric nanostructures fabricated through self-assembly are studied. In this paper, we synthesized the neodymium substituted Bi₄Ti₃O₁₂ nanostructures on Pt/Ti/SiO₂/Si substrates. The method we used here was spin coating precursors with a series of different concentrations on the substrates and then annealing at 750 °C in the oxygen atmosphere to get the self-patterning nanoparticles. In order to avoid the influence of the Pt/Ti/SiO₂/Si substrates to the largest extent, the substrates were annealed first for different time in oxygen atmosphere to select appropriate conditions. Scanning probe microscope, and X-ray diffraction were used to detect the morphology and the crystalline structure of the nanoparticles respectively. The well-separated Bi_3.15Nd_0.85Ti₃O₁₂ particles have a typical lateral size about 100–150 nm and height about 20–25 nm. XRD reveals pyrochlore phase in the low concentration samples. The lower the precursor’s concentration, the higher the excess of Bi element is needed to form the pure perovskite nanoparticles.     

Size control of Pb-based glass powders between 38 and 84 nm in the flame spray pyrolysis

Nano-sized Pb-based glass powders with different mean size, ranging from 38 to 84 nm were prepared by flame spray pyrolysis. The mean sizes of the glass powders were controlled by changing the concentration of spray solution. The glass powders prepared by flame spray pyrolysis from the spray solutions with different concentration had broad peaks at around 28° in the XRD patterns. The dielectric layers formed from the glass powders with the mean size of 38 nm had dense inner structures at firing temperatures of 480 and 520°C. On the other hand, the dielectric layer formed from the glass powders with the mean size of 84 nm had some voids inside the layer. The transmittances of the dielectric layer formed from the glass powders with the mean sizes of 38 and 84 nm were each 91% and 74% at firing temperature of 480°C.     

A Novel Alkali-activated Magnesium Slag-based Nanocomposite for Photocatalytic Production of Hydrogen

Alkali-activated magnesium slag-based nanocomposite (AMSN) by loaded about 5wt% CuO was synthesized and firstly employed as a novel catalyst for production of hydrogen by photocatalytic water-splitting. The XRD and XPS results indicated that there was principally mineralogical phase of calcium silicate hydrate (CSH) in AMSN, and CuO with a mean particle size of 15 nm dispersed on the surface of AMSN. The UV–visible diffuse reflectance spectrum and photoluminescence spectrum revealed that the CuO/AMSN sample showed a strong absorption edge at 1.4 eV and a weak photoluminescence peak at 394 nm, respectively. The CuO/AMSN catalyst showed the highest H₂ evolution in amount of 102.95μL/g by photocatalytic water-splitting for 6 h due to the synergistic effect between CSH skeleton network and CuO nanoparticles. A mechanism of photocatalytic H₂ production was suggested.     

Influences of starting particulate materials on microstructural evolution and electrochemical activity of LSM-YSZ composite cathode for SOFC

LSM-YSZ composite electrodes are prepared from a mixture of YSZ and LSM particles. Commercial YSZ particles were mixed with polymerizable complex method-driven LSM powders of two different particle sizes, 81 and 210 nm. The correlations between sintering temperature, microstructure and performance of composite cathode have been studied. It was found that optimum sintering temperature differs depending upon the LSM particle size. The composite cathode derived from finer LSM particles displayed lowest polarization resistance ∼0.46 Ωcm² when sintered at 1100^∘C, whereas the same resistance was observed for the electrode involving larger LSM sintered at 1200^∘C. The microstructural changes evolved during the course of sintering and the resulting electrodes were investigated by scanning electron microscopy and impedance spectroscopy.     

Unique Growth and Optical Behaviors of Chromium Doped ZnSe Nanoparticles Induced by ns Laser Pulse

We have synthesized chromium doped ZnSe nanocrystalline particles (Cr²⁺:ZnSe NCPs) by using nanosecond pulsed laser ablation of polycrystalline Cr²⁺:ZnSe micron-sized powder in liquid environment. The scanning electron micrscope and X-ray diffraction results reveal that the products are ZnSe cubic sphalerite structure with an average size around 60 nm. Based on the Cr²⁺:ZnSe nanoparticles, typical random laser emissions centering at 2175 nm with a threshold of 0.4 mJ/pulse were observed. Compared to the Cr²⁺:ZnSe bulk laser, the central wavelength shows a ～175 nm blue-shift. The photoluminescence lifetime of Cr²⁺:ZnSe NCPs is shorter than that of Cr²⁺:ZnSe bulk.     

Electrical conductivity of ceria nanoparticles under high pressure

This paper describes the electrical conductivity of ceria nanoparticles under high pressure ranging from 2 to 6 GPa. The samples used were pure and acceptor-doped ceria nanoparticles with a grain size of approximately 2 nm prepared by mixing hexamethylenetramine and metal nitrate solutions. The size of ceria nanoparticles was controlled to be 2 to 15 nm by varying heat-treatment conditions. The in-situ electrical conductivity measurements under high pressure were conducted by using an ac-impedance spectroscopy. By applying a pressure of 6 GPa at 300 °C, the green compact of 6 mol % Sm-doped ceria nanoparticles was densified; a relative density of 93% was achieved. The sample showed an electrical conductivity of 3?×?10^???3 S/cm at 300 °C under 6 GPa. The enhancement of electrical conductivity under high pressure seems to be related to ionic conduction in the vicinity of grain boundaries.     

Characteristics of silver powders synthesized from silver 2-ethylhexanoate and Di-n-octylamine

Uniform spherical submicron silver powders were synthesized from a long-chain alkyl carboxylate of silver 2-ethylhexanoate and an alkylamine of di-n-octylamine in this study. The decomposition of silver 2-ethylhexanoate was observed to accelerate significantly in the presence of di-n-octylamine. SEM results revealed that submicron silver powders with sizes ranging from 200 nm to 300 nm and a high tap density of 4.0 g/cm³ were successfully prepared at 150 °C for 3 h in air. TGA reveals that approximately 1.2 wt.% organic residues composed mainly of 2-ethylhexanoate with a slight amount of di-n-octylamine were attached to the silver particles, as confirmed by the FTIR and XPS results. To evaluate the feasibility for practical applications, silver paste prepared from the silver powders synthesized in this study (NAG 80 paste) was examined and characterized, and the results were compared with those of two commercially available powders (SF80 and GH67 pastes). The electrical resistivities of the NAG80 films fired at 300 and 500 °C respectively read 1.8?×?10^?5?Ω-cm and 1.1?×?10^?5?Ω-cm, both superior to those of the SF80 and GH67 films. The fine quality of the uniform submicron spherical silver powders was verified and its potential use in thick film conductors confirmed.     

Synthesis and properties of SDC powders and ceramics for low temperature SOFC by stearic acid process

Ce_0.8Sm_0.2O_1.9 (SDC) powders were prepared by a novel solution combustion process using molten stearic acid as dispersive medium and reducing agent. The powders prepared with the molar ratio of $ {\text{NO}}^{ - }_{{\text{3}}} $ to stearic acid at 1:1.5 exhibited a narrower distribution in sizes and the average agglomerate size is about 157 nm. The non-agglomerated particles are in the range 10–40 nm. The as-combusted powders prepared by the present method were pure oxides powder with low crystallinity, which exhibited excellent sintering properties, easily achieving high dense SDC ceramics with lager grains (0.85 μm).     

Surface modification of nanoscale iron carboxylate metal organic framework with polyethylene glycol

ABSTRACT

MIL-101-Fe (Materials of Institute Lavoisier) metal organic framework (MOF) was synthesized by solvothermal method. Further, surface of the as prepared MIL-101-Fe is with Polyethylene glycol (PEG). FESEM and TEM micrograph of MIL-101- Fe and PEGylated MIL-101-Fe particles showed hexagonal shaped morphology with particle size in the range of 400–500 nm and 600-700 nm respectively. The DLS spectra also show the similar results. This increase in size of the particles indicates the presence of PEG layer on the surface of the MOFs. FTIR characterization was further conducted to detect the functional groups of the MIL-101(Fe) and after PEG coating. These results confirm the presence of PEG in MIL-101(Fe) framework.     

Magnetic properties and thermal behavior of mullite–iron nanocomposite powders

Mullite based iron magnetic nanocomposite powders were synthesized by reduction of sol–gel prepared mullite–iron oxide solid solution in hydrogen flow. Structural characterization studied by TEM revealed that two types of α-iron nanoparticles existed in mullite matrix. The α-iron nanoparticles with the size around hundreds of nanometers appeared as inter-type grains, while those around 10 nm were embedded in the grains of mullite. The magnetic properties of nanocomposites suggest that the intergranular and intragranular α-iron nanoparticles had the ferromagnetic and superparamagnetic behavior at room temperature, respectively. The oxidation behavior of nanocomposite powders showed that there existed two different oxidation stages of α-Fe nanoparticles.     

Synthesis of nanosized (1 − x)BiScO3 − xPbTiO3 ferroelectric ceramic powders

Nanosized (1???x)BiScO₃???xPbTiO₃ ferroelectric ceramic powders was obtained by the metal citrate sol–gel method. The decomposition process of the polymer was studied by using infrared spectral absorption and X-ray diffraction. Perovskite phase can be obtained at the calcining temperature as low as 450 °C and the average grain sizes of powders were calculated by XRD method. The influence of the grain size by pH value of the solution is explained. The calcining temperature is proved to be the foremost factor to determine the grain size which grew from 12 to 23 nm when calcined at different temperatures. The holding time can also affect the grain size. The sintering temperature can be reduced by 100 °C using nano powders than using traditionally prepared large grain powders.     

Phase and microstructural evolution of Sn particles embedded in amorphous carbon nanofibers and their anode properties in Li-ion batteries

Phase and microstructural evolution of Sn-Carbon composite nanofibers (NFs) under various heat treatment conditions was clearly demonstrated in this work. Amorphous carbon nanofibers (a-CNFs) that contained metallic Sn nanoparticles were prepared via electrospinning and subsequent calcination under a reducing atmosphere. The sizes of the metallic Sn particles, which were decorated inside and outside of a-CNFs, were precisely manipulated by varying the Sn precursor content and introducing a reinforced quenching step, i.e., controlling the cooling rate after high-temperature processing. Because of the low melting temperature of metallic Sn (231.9 °C), the nucleation and growth rates of the Sn nanoparticles were significantly influenced by the high-temperature processing and cooling condition. In particular, the stresses that originated from volume changes of the Sn nanoparticles during the lithium alloying and dealloying processes were effectively compensated by amorphous carbon containing Sn particles, which led to reduced structural damage. The morphologies of the fibers with incorporated Sn nanoparticles provided efficient permeability to allow the penetration of the electrolyte into the inner fiber structure while maintaining a high-capacity (950 mAh g^?1 at 0.5 C-rate) characteristics due to enhanced surface activity.     

Nanoblast synthesis and SPS of nanostructured oxides for SOFC

Engineering of Cerium Gadolinium Oxide (CGO) and Yttria Stabilized Zirconia (8Y-SZ) ceramic nanopowder with precise morphology and homogeneity of the compounds by multiple nanoblast technique of preliminary engineered nanoreactors was analysed. Nanoreactors were produced by morphology optimization technique and loaded by colloidal impregnation of the C₃H₆N₆O₆. The subsequent explosive initiation of C₃H₆N₆O₆ followed thermal detonation form gaseous products with local temperatures of ~2500°C. The rapid evolution of a large volume of gaseous products i.e. impacts of the blast waves dissipates the heat of the process and limits temperature increase, thus reducing the possibility of premature local partial sintering among the primary particles; and leads to the fragmentation of the surrounding agglomerates. Uniformly aggregated nanosize CGO and 8Y-SZ consisting of ~50 nm nano-aggregates of ~7 nm crystallites with a remarkably homogeneous composition and uniform morphology were synthesized. The SPS consolidation of nanosized aggregates of 8Y-SZ and CGO was analyzed. The 8Y-SZ ceramic with an average grain size of 90 nm and CGO nanoceramic with average grain sizes of 73, 32 and 12 nm were obtained by SPS at 1100, 1035 and 970°C, respectively under the pressures of 90–150 MPa.     

Preparation and Evaluation of Phenylethyl Resorcinol Liposome

Phenylethyl Resorcinol liposome for cosmetic application was developed to enhance the water solubility and physicol stability. Relevant data showed that samples were kept stable for at least 90 days. The liposome showed a spherical morphology under transmission electron microscope and the particle sizes were in the range of 160–170 nm. The zeta potential was ?63.7 mV at dilution 20 times and drug-loading rate was 2.45 ± 0.03%. Conclusively, Phenylethyl Resorcinol liposome has very promising potential in cosmetic industry.